Abrading wheels



Oct. 6, 1959 v. L. SHEETS ABRADING WHEELS- Filed Oct. 23, 1956 i? Q: 21g. 5

INVENTOR VERNAL L. SHEETS BY PHI" 5 Usually,

United States Patent ABRADING WHEELS Vernal L. Sheets, Valparaiso, Ind.,assignor to Chicago Wheel & Manufacturing Company, Chicago, 111., acorporation of Illinois Application October 23, 1956, Serial No. 617,8302 Claims. (Cl. 51-206) This invention relates to mounted abradingwheels, and in particular to abrading wheels comprising a vitreousbinder affixed to a steel mandrel.

Abrading wheels of the kind to which the present invention relates arecomposed of finely divided abrasive material such as alumina, siliconcarbide or the like bonded by a fused vitreous binder material. Such anabrading wheel is to be afiixed to a metallicmandrel to afforda-so-called mounted abrading wheel, and the mandrel at the free endthereof is adapted to be secured in a power tool incidental to using theabrading wheel for the desired polishing or grinding operation.

The commonly adopted method of manufacturing mounted abrading wheels hasentailed pressing in a die cavity under relatively high pressure thecomposition that is to afford the wheel, such composition including anabrasive material and a binder for the abrasive. The die cavity iscomplemental to the wheel to be formed, and usually the composition forthe wheel has been pressed about a fixed core or insert in the diecavity affording a bore in the compacted .wheel composition. The wheelcomposition thus provided with a bore is removed from the die cavity andfired, that is, subjected to heat to produce fusing of the binder topermanently bond together the abrasive particles. Next, the bore in thewheel is swabbed with cement, or the end of the mandrel to be joined tothe wheel is provided with cement, and the mandrel is then inserted inthe bore of the finished wheel. the cement is of a nature requiring aheat cure to effect the desired bond between the wheel and the mandrel.

Alternatively, the wheel may be formed and fired, and then drilled toafford a bore for the mandrel.

It will be seen from the foregoing that the commonly adopted methods ofmanufacturing mounted abrading wheels have entailed individual mountingof a mandrel in the bore of the related abrading wheel having apreformed bore. It is known that such individual mounting of the mandrelinvolves numerous rejects, and therefore a substantial overhead, due toinaccurate alignment of the mandrel, and this is particularly so inthose instances where the cement used to afiix the mandrel to the wheelrequires a heat cure, since during the heat cure cycle the cementcommonly used undergoes an intermediate softening stage which encouragestilting of the mandrel out of true. Therefore, in the absence of specialprecautions, an unusually large number of rejects are encountered inmanufacturing mounted abrading wheels according to either of theforegoing methods, and it will be appreciated that clearance is requiredbetween the diameter of the mandrel and the diameter of the bore of thewheel because otherwise there would be an unacceptably low clearancevolume for the cement used to join the mandrel to the wheel. It is thisneed for clearance volume which introduces the uncertain aspect ofmandrel alignment mentioned above.

it of course would be desirable to integrate the wheel 2 and the mandrelin one operation as by pressing the loose composition for the wheeldirectly about the aflixing end of the mandrel, and this method ofproduction is in fact feasible in those instances where the binderincluded in wheel at the time the abrasive composition is compacted'ture which at least discolors a stainless subsequent heating of theassembly including the wheel and the mandrel is required in order to setthe binder, whether the binder be resinous or vitreous, and thetemperature used to thus set the binder could not be so high as toadversely affect the mandrel. thermosetting resin setting or curing letus say at 500- 600 F. enables firing of the assembly to be accomplishedat temperatures having no adverse effect on the mandrel, but such methodof production of mounted abrading wheels involving union of the mandreland the compacted but unfired abrasive composition in the first instanceis not feasible where temperatures required to set the binder are in theneighborhood of 2000 F., a temperasteel mandrel and which adverselyaffects the grain structure of plain, that is unalloyed carbon steel,and which often causes warping of the mandrel due to thermal softeningof the mandrel.

The primary objectvof the present invention is to enable mountedabrading wheels to be manufactured having a steel mandrel united to theabrading wheel at the time the abrasive composition is compacted to formthe wheel and wherein the abrasive composition includes a vitreousbinder. Specifically, it is the object of the present invention tomanufacture abrading wheels having an abrasive composition includinglead borosilicate glass as a binder by compacting the composition in adie cavity about the aflixing end of a steel mandrel disposed in the diecavity, and to fire, that is, heat the thus-united parts including thewheel and the mandrel at a temperature around 1200 P. which issufiicient to fuse the binder to produce the desired binding of theabrasive particles and permanent union of the abrading wheel to themandrel. In other words, the present invention makes possible productionon a commercial scale of-mounted abrading wheels including a steelmandreland a wheel having a vitreous binder, which haslong been an aimof the art. One important aspect of the present invention is that themethod of manufacture herein involved enables a mandrel to be usedhaving an enlarged head at the wheel afiixing end thereof, so that theaccomplishment of this is a further object of the present invention.Thus, the use of a mandrel having an enlarged head at the; end to beafiixed to the abrading wheel has heretofore not been capable ofsatisfactory accomplishment; in connection with an abrading wheelincluding a vitreous binder where separate manufacture of the wheel andthen individual mounting of the related mandrel in the bore In otherwords, a

into the abrading wheel in such a manner that there is a full andcomplete complemental or interfacial mating of the parts.

Other and further objects of the present invention will be apparent fromthe following description and claims and are illustrated in theaccompanying drawings which, by way of illustration, show a preferredembodiment of the present invention and the principle thereof and what Inow consider to be the best mode in which I have contemplated applyingthat principle. Other embodiments of the invention embodying the same orequivalent principles may be used and structural changes may be made asdesired by those skilled in the art without departing from the presentinvention and the purview of the ap pended claims.

In the drawings:

Figs. 1 to 4 inclusive are schematic sectional views of a pressillustrating progressive stages of manufacture of a mounted abradingWheel in accordance with the present invention preliminary to firing theabr'ading wheel and the mandrel that is affixed thereto;

Fig. 5 is a schematic sectional view showing firing of assemblies takenfrom the press;

' Fig. 6 is a perspective view of a completed mounted abrading wheel ofthe kind contemplated by the present invention; and

Fig. 7is a sectional view taken substantially on the "line 7-7 of Fig.6.

The present invention is illustrated in the drawing as pertaining to theproduction of mounted abrading wheels as 10 shown in Figs. 6 and 7 ofthe drawing, such mounted abrading wheels comprising a mandrel 11 havingan abrading wheel 12 affixed'to one end thereof. As shown in Figs. 2 and7 of the drawing, the mandrel 11 in accordance with the presentinvention is formed at the affixing end there'of'with an enlargedannular head 13. inwardly of the head 13, the afiixing end portion ofthe mandrel is reduced in diameter at 15 to afford an upper or outerannular shoulder 16, and preferably this reduced portion of the mandrelis knurled at K or otherwise provided with ribs and grooves to in effectincrease the area of the mandrel that is 'afiixed to the abrading wheel.The end of the knurled or reduced portion'of the mandrel opposite theshoulder 16 is further defined by a lower or inner annular shoulder 17which also represents the inner end ofthe shank portion of the mandrelwhich is adapted to be fitted in a chuck or the like of a power tool. Itwill be recognized from Fig. 7 that the abrading wheel 12 is fullycomplemental to the portion of the mandrel l1 surrounded-by theabrading' wheel, that is, the abrading wheel and mandrel meet at aninterface which is fully .complemental to the enlarged head 13 of themandrel, the reduced or the knurled portion 15 and the lower shoulder17. Under the present invention, the abrading wheel comprises the usualfinely divided abrasive, and the abrasive particles are bonded togetherby a vitreous binder which also serves to bind the abrading wheelpermanently to the affixing end of the mandrel.

' The affixing end of the mandrel defined in the foregoing manner can beconveniently afforded by machining the stock for the mandrel. As anexample, the stock may i be one-quarter inch in diameter, which will bethe diameter of the head 13 and the shank portion of the mandrel to befitted in a power tool, and the knurled portion 15 will be reduced byone to three thirty seconds of an inch.

T he method of production under the present invention is illustrated inprogressive stages in Figs. 1 to 5 of the drawing, and to this end thereis used a press embodying a cylindrical outer sleeve 20 defining acylindrical mold cavity 21open at one end 22. The opposite end of themold cavity 21 is adapted to 'be closed off by a cylindrical block 25having an elongated bore 26, the block 25 being partially inserted inthe mold cavity 21 from the lower end thereof. It will be observed inFig. 1 that the bore 260f the block 25 opens at both ends of the block25.

The first step incidental to production of a mounting abrading wheel 10in accordance with the present invention is to dispose the mandrel 11 inthe bore 26 of the block 25 so that the affixing end of the mandrelprojects into the die cavity as shown in Fig. 2. It is preferred thatthe mandrel be so positioned that the shoulder 17 be disposed within thedie cavity sufiiciently to expose a portion of the shank of the mandrel11 below the shoulder 17 to the die cavity. This is convenientlyaccomplished by use of a plug 28, Fig. 2, disposed in the bottom of thebore 26 of the block 25 so to afford a fixed support for the lower endof the mandrel 11 with the afiixing or upper end of the mandrelprojected the desired amount into the die cavity 21.

The loose, granulated abrasive composition that is to afford the wheel12 of the mounted abrading wheel is next used to fill the die cavity 21to the required depth as shown in Fig. 3, and under the presentinvention this composition comprises 70 to percent by weight abrasiveparticles such as alumina, silicon carbide or the like of desiredparticle size, andaccordingly 5 to 30 percent by weight of powdered leadborosilicate glass of approximately 325 mesh. The following is anexample in accordance with the foregoing:

EXAMPLE 1 Material: Parts by weight Abrasive particles 70-95 Binder(Example 2) 30- 5 EXAIVIPLE 2.-BINDER Lead borosilicate glass Silica r-37.6 Boric acid 5.9 Red lead oxide 46.5

To afford a temporary binder for the abrasive composition, the permanentbinder ingredients of Example 2 above are mixed with silicate on thebasis of approximately one part by weight of sodium silicate to 3 /2parts by weight of the lead borosilicate-glass. It may here be mentionedthat the proportion of abrasive particles to binder of Example 2 willdetermine the desired hardness of the wheel, that is,the hardness of thewheel will vary in a direct ratio with the amount of binder materialused;

After the die cavity has been filled to the desired extent as shown in.Fig. 3, predetermined of course according to the desired axial dimensionof the finished product, the abrasive composition is subjected topressure by a ram 30, Fig. 4, entering the die cavity 21 from the openend 22 thereof, and this ram has a predetermined pressure and strokesufiicient to compact the loose abrasive composition in the die cavity21 to the desired density and thickness. Following this operation, theram 30 is withdrawn and'the abrasive composition has been sufiicientlycompacted to enable the wheel and mandrel to be handled as an assembly.

Each assembly removed from the die cavity is in a green, that is unfiredstate inasmuch as the abrasive composition is only compacted and thebinder has not as yet been vitrified, but nevertheless the pressuresentailed during compaction of the abrasive composition in the die'cavity21'were sufiicient, together with the sodium silicate temporary binder,to cause temporary adhesion of the abrasive composition and cohesion ofthe unfired wheel to the mandrel. r

As shown in Fig. 5, a heat treating furnace is illustrated at FR,and'the unfired assemblies 1OU that are to be fired are arrangedtherein. Any desired source of heat can of course be used, and theexpression fired is used generically herein broadly to designate theheat treating operation as entailing heating of the assemblies IOU tocause fusion or vitrification of the lead borosilicate glass binderparticles producing permanent bonding of the abrasive particlescomposing the abrading wheel and a permanent union of the abrading wheelto the aflixing end of the mandrel. Based on the foregaing examples,each assembly as it is removed from the die cavity 21 is first allowedto dry in air to at least partially dry the sodium silicate temporarybinder, and then each assembly is fired as in a furnace PR for a minimumof four hours with a maximum temperature of 1200" F. Thus, in accordancewith the present invention, relatively short heating cycles are entailedat relatively low temperatures in comparison to cycles of nearly fortyhours at temperatures Well in excess of 1200 F. as formerly used inproducing mounted abrading Wheels having a vitreous bond. Of particularimportance in the present instance is the fact that the low firingtemperatures involved do not adversely affect a mandrel of stainlesssteel or a mandrel of plain carbon steel.

Hence, while I have illustrated and described the preferred embodimentof my invention, it is to be understood that this is capable ofvariation and modification and I therefore do not wish to be limited tothe precise details set forth, but desire to avail myself of suchchanges and alterations as fall Within the purview of the followingclaims.

Iclaim:

1. A mounted abrading wheel comprising a mandrel, said mandrel beingcomposed of steel and having an attaching end portion, and an abradingwheel bonded complementally and interfacially directly to and in contactwith said attaching end portion of the mandrel, said abrading wheelbeing composed primarily of abrasive particles in an amount of aboutseventy to ninety-five parts by weight of the abrading wheel, theremainder of the material in the abrading wheel consisting of arelatively low melting point lead borosilicate glass binder consistingof silica, boric acid and red lead oxide fused to form a matured glassbinder which binds together the abrasive particles and binds the wheelto the mandrel. 2. A mounted abrading wheel according to claim 1 whereinthe steel mandrel is selected from the group consisting of stainlesssteel and plain carbon steel.

References Cited in the file of this patent UNITED STATES PATENTS201,910 Caesar Apr. 2, 1878 1,458,772 Marry June 12, 1923 1,499,345Chott July 1, 1924 2,248,990 Heany July 15, 1941 2,281,525 Milligan etal Apr. 28, 1942 2,324,377 Fischer July 13, 1943 2,454,068 Kuhlman Nov.16, 1948 2,479,079 Ried Aug. 16, 1949 2,763,970 Miller et al Sept. 25,1956

